Conjugated polymers and nature-derived molecules for light-emitting electrochemical cells and acidochromism

Doctoral thesis, 2026

Organic electronics have been dynamically developing in the last decades, garnering attention both within academia and industry for a variety of applications. While the most spectacular success story so far is organic light-emitting diode (OLED), a closely related technology light-emitting electrochemical cell (LEC) has been developed as a promising alternative.By the merit of simpler device structure and in situ electrochemical doping, LECs offer a pathway toward easily manufactured, printable lighting solutions that better exploit the inherent processability of organic materials. However, LECs still require further research and development to match the performance of already commercialised OLEDs. In this work, three projects with focus on LECs were conducted. Firstly, the possibility of using natural pigments as emitters was explored. A method for efficient, scalable extraction and separation of chlorophyll a was developed and the first reported chlorophyll-based LEC was fabricated. In the second project, white-emitting LECs were designed, with emission coming from a single component. By synthesising a copolymer incorporating red, green and blue fluorophores at an optimised ratio, the issue of phase separation and colour drift were avoided. The third project addressed the issue of aggregation-caused quenching in conjugated polymer LECs. It was shown that the modification of side chains alone may not be sufficient to prevent strong backbone aggregation and fluorescence quenching. Significant improvement in performance was achieved by the introduction of order-disrupting comonomer into the main chain without compromising the emission profile. In the last part of the thesis work, polymers with optoelectronic properties dependent on the presence of acid in the environment (i.e. acidochromic) were synthesized and studied. Characterisation of the acidochromic behaviour combined with DFT calculations provided insight into the mechanism of acidochromic response for azo-, imine- and vinyl-bond-containing polymers. In summary, this thesis focuses on multiple approaches to advance the LEC technology, by promoting the use of natural pigments, the implementation of copolymers as single-component white emitters and investigating methods to mitigate aggregation-caused quenching.